The purpose of this study is to develop techniques for studying central nervous system monamine metabolism in man, and to carry out pharmacokinetic studies of psychoactive drugs. Studies of the kinetics and clearance of deuterated homovanillic acid (HVA) from the circulation were conducted in rhesus monkeys and patients. In primates, calculated basal rate of HVA production by the entire animal was 5.2-12.6 mg/kg/hr. Less than one percent of HVA in CSF is derived from blood, and HVA in urine is derived only from blood, not from renal metabolism of dopamine. Infusion of probenecid indicated that approximately 70% of total body HVA originated in the CNS. An assay for dopamine sulfate has been established. Studies are in progress on pharmacological effects on CSF norepinephrine. Plasma levels, pharmacokinetics, and renal clearance of phencyclidine (PCP) are under investigation.